Role of Tim4 in the regulation of ABCA1+ adipose tissue macrophages and post-prandial cholesterol levels.

Dyslipidemia is a main driver of cardiovascular diseases. The ability of macrophages to scavenge excess lipids implicate them as mediators in this process and understanding the mechanisms underlying macrophage lipid metabolism is key to the development of new treatments. Here, we investigated how adipose tissue macrophages regulate post-prandial cholesterol transport. Single-cell RNA sequencing and protected bone marrow chimeras demonstrated that ingestion of lipids led to specific transcriptional activation of a population of resident macrophages expressing Lyve1, Tim4, and ABCA1. Blocking the phosphatidylserine receptor Tim4 inhibited lysosomal activation and the release of post-prandial high density lipoprotein cholesterol following a high fat meal. Both effects were recapitulated by chloroquine, an inhibitor of lysosomal function. Moreover, clodronate-mediated cell-depletion implicated Tim4+ resident adipose tissue macrophages in this process. Thus, these data indicate that Tim4 is a key regulator of post-prandial cholesterol transport and adipose tissue macrophage function and may represent a novel pathway to treat dyslipidemia.

Histology and Immunohistochemistry of the Cardiac Ventricular Structure in the Green Turtle (Chelonia mydas).

This study describes the implications of cardiac ventricular microscopy in Chelonia mydas relating to its ability to dive. For this work, 11 specimens of the marine turtle species C. mydas found dead on the coast of Rio Grande do Norte (Northeast Brazil) were used. After necropsy, fragments of the cardiac ventricular wall were fixed in 10% buffered formaldehyde solution for 24 h and then subjected to routine processing for light and scanning electron microscopy (SEM). The ventricle in this species is formed by the epicardium, myocardium and endocardium. The subepicardial layer consists of highly vascularised connective tissue that emits septa to reinforce the myocardium surface. There is an abundant and diffuse subepicardial nerve plexus shown by immunostaining technique. The thickness of the spongy myocardium and the nature of its trabeculae varied between the heart chambers. The endocardium shows no characteristic elements of the heart conduction system. The valves have a hyaline cartilage skeleton, coated by dense irregular connective tissues characterised by elastic fibres. These findings in the green turtle ventricular microscopy are related to hypoxia resistance during diving.